Circuit for amplifying electric oscillations



March 1943. A. VAN DER ZlEL ETAL 2,312,509

CIRCUIT FOR AMPLII'YING ELECTRIC OSCILLATIONS Filed May '7, 1941 I AAAAA vvvvv AAAAA vvvv I AAAAA vvvv INVENTORS ALBERT VAN DER ZIEL gek/vsu s. NOL

A'ITORNEY invention.

The known amplifier arrangement of Fig; 1

v Patented Mar. 2, 1943 CIRCUIT FOR AMPIJFYIN G ELECTRIC OSCILLATIONS Aldert van der Ziel: and Korneiis' "Swier 'Knol, Eindhoven, Netherlands; vested in the Alien Property Custodian Application May 7', 1941, Serial No. 392,202

'In the Netherlands June '4, 1940 7 Claims. (01.1'79-1'11) This invention relates to a circuit arrangement for amplifying electric oscillations, more particularly oscillations having a wavelength of less than 10 meters.

In the drawing, Fig. 1 shows-a known circuit arrangement which will serve to explain the present invention, and Figs. 2, 3 and,4 are circuits which illustrate two,embodiments of the present comprises a discharge tube I having a cathode 2,

a control grid 3, a screening grid 4 and an output electrode 5, the screening grid 4 being given a high positive bias and'the outputjlectrode 5 a feeble positive or negative bias. 3 Intermediate the control grid "3 and the cathode'2 there is provided an input impedancei to which the oscil-* lations tobeamplified are fed, whereas the out} put electrode 5 and the cathode 2 have interconnected between them an output impedance! from which the amplified oscillations are derived.

The operation of this known circuit is based on the fact that intermediate the screening grid 4 and the output electrode 5 is formed a space charge whosedensity is governed by the alternating voltage active at the .control grid. This space charge-induces in the output electrode a corresponding positive image charge whose intensity depends on the alternating voltage operative at the controlgrid and gives rise to the occurrence.

of an amplified voltageacross the'output impedance 1.

When oscillations having a wavelength, below has the disadvantage th'at a virtual ohmic re. sistance of comparatively low value occurs betweenthe output electrode 5 and the cathode 2 and gives rise to a heavy damping of the output circuit; This heavy output damping renders the relevant circuit arrangement less suitable for the amplification of ultra high frequencies.

According'to the invention, this disadvantage is obviated by the use of a perforated output electrode and by the arrangement of .one or more fact that by reason oi the use of a perforated.

output electrode and beyond it of a positive electrade the output damping is considerably reduced and may even become negative. V

In order that the invention may be more clear- 13; understood and readily carried into effect it differentiated from will now be described more fully with reference to Figs. 2-and 3.

The circuit arrangement shown in Fig. 2 is the known arrangement shown in Fig. 1 in that the output electrode 5 which, similarly to the arrangement shown in Fig. 1"is given a negative bias, is constructed in the shape of a grid and beyond it is arranged an electrode 8 which is =earthed so far as high frequencies are concerned through a condenser 5 and to which a positive bias is supplied through a resistance l0. v

Thus, a materially lower damping than in the known circuit arrangement occurs between the output electrode 5 and the cathode 2 and this damping may even be rendered negative by a suitv able choice of the bias'of the output electrode 5.

It is obvious that this renders possible considerably greater amplification of ultra-high frequency oscillations than can be obtained in the known arrangement.

The occurrence of a negative output. damping in the arrangement shown in Fig. 2 may be due tothe following. If a high negative bias is ap- 5 plied to the electrode 5 all the electrons passed '10 meters are amplified this circuit arrangement 35 by the screening grid 4 will reverse their direction before't'he electrode 5. The reversing electrons form a space charge in front of the electrodei which induces a corresponding positive image charge in the electrode 5. If the bias of the electrode 5 is rendered less negative, then a part of the arriving electrons will be passed by the electrode 5 so that the said space charge is reduced and consequently a lower positive charge 'occurs in, the electrode 5. There is consequently E a range of biases o the electrode 5 in which the chargeof this electrode becomes-less positive if thebias is rendered more positive. In this range the elec rode 5 has therefore a negative capacity 0 relatively to the cathode so that if an alternating voltage is applied to the electrode 5 a current 'will flow to the cathode which lags by with respect to the voltage. This current is transmitted by the electrons which flow .from the cathode to the space charge occurring in the neighbourhood of the electrode '5. In the case of ultra-high frequencies the transit time of the electrons from the cathode to the space charge will be of the same order of magnitude as the period of the oscillations to beamplifled so that the transmis-- sion of the said current will be effected with at. noticeabletime lag. The current will thus manifest a greater lag than 90, 1. e.. it will contain a component which is in antiphase with the voltage'appliedto the electrode. This component v tions from a source II and the circuit I2 is amplification of ultra-high frequencies by means of a single tube.

One example of this embodiment of the invention is shown in Fig. 3. The electrode 8 is constructed as a screening grid and beyond it' is arranged an anode II which is connected to the cathode with the interposition of an oscillatory' circuit l2 tuned to the frequency of the oscillations to be amplified. The singly amplified voltage across the circuit '1 is amplified once more in the part of the tube formed by the electrodes 5, 8 and l I so that a double amplified voltage can be derived from the circuit H. In this circuit arrangement use may be made of a hexode, a pentagrid or an octode of the usual type, the oscillations to be amplified being fed to the first control grid, the circuit of the secondcontrol grid whose negative bias is preferably such that a negative resistance occurs between this control grid and the cathode including an oscillatory circuit tuned to the frequency of-the oscillations to be amplified and thedoubly am-' plified output voltage being obtained from the anode. I K

The circuit arrangement shown in Fig.3 may be .used as a mixing stage in a superheterodyne receiver. For this purpose, as shown in Fig. 4

cuit'connected between the control grid and cathode, means for impressing a .high positive bias on the screen grid and said additional electrode, an output circuit connected between the perforate output electrode, and means for impressing a negative or output electrode.

4. A: circuit arrangement as defined in claim 3. wherein the input and output circuits are resonant circuits tuned to the frequency to be amplified, and the additional electrode disposed on the side of the output electrode remote from the cathode is connected to ground with respect to high frequencies.

5. Acircuit arrangement for the amplification of ultra-high frequency oscillations, particularly oscillations having a wave length less than 10 meters, comprising an electron discharge tube which is the same as Fig. 3 except for the portion to' the right of the dash line a:-a:, the circuit of the electrode 5 includes, for example in series with the circuit 1, an impedance I3 across which there is impressed the locally generated oscillatuned to the intermediate frequency.

We claim: l. A circuit arrangement for the amplification of ultra-high frequency oscillations, comprising an electron discharge tube having at least a cathode, a control grid, a screen grid, at perforate output electrode and one or more additional electrodes disposed in the order named, means for impressing a high positive bias on the screen grid and the one or more additional electrodes, and means for impressing a negative or low positive bias on the output electrode.

2. A circuit arrangement as defined in claim 1, wherein the bias of the-perforate output electrode is such that anegative resistance occurs between said output electrode and the cathode.

3. A circuit arrangement for the amplification of ultra-high frequency oscillations, comprising an electron discharge tube having atleast a and an imperforate output electrode, an input with respect to said high frequency oscillations.

cathode, a control grid, a screen grid, a perforate output electrode and at least one additional electrode disposed in the order named, an input cirhaving at least a cathode, a control grid, a screen grid, a-perforate electrode, a second screen grid and an imperforate output electrode disposed in the order named, a first resonant circuit connected between the control grid and cathode, a second resonant circuit connected between the perforate electrode and cathode, a third resonant circuit connected between the imperforate output electrode and cathode, the first and third circuits constituting respectively the input and output circuits and all three resonant circuits being tuned to the frequency of the oscillations to be amplified, means for impressing a high positive bias on the screen grids and the imperforate output electrode, and means for impressing a negative or low positive bias on the perforate -cludes an impedance across which are developed locally generated oscillations of a frequency differing from the frequency of the oscillations to be amplified, and the output circuit connected to the imperforate electrode is tuned to the difference or intermediate frequency. e

. 7. A circuit arrangement for the successive amplification of ultra-high frequency oscillations, ,particularly oscillations having a wave length less than 10 meters, comprising an electron discharge tube having arranged in the order named at least a cathode, a control grid, a screen grid, a perforate electrode, a second screen grid circuit tuned to the frequency of the oscillations tobe amplified connected to the control grid,

second and third circuits tuned to the same 'frequency as, the input circuit connected respectively to the perforate and imperforate electrodes, meansfo'r impressing a high positive 'biason the screen grids and the imperforate output electrode, means for impressing a negative or low positive bias on the perforate electrode, and means for connecting the screen grids to ground ALDERT VAN DER, ZIEL.

KORNELLS swma apron low positive bias on said 

